Mitsuru Watanabe

Effects of Buckwheat Sprouts on Plasma and Hepatic Parameters in Type 2 Diabetic db/db Mice

We examined the effects of buckwheat sprouts (BS) (Fagopyrum esculentum Moench) on lipid and carbohydrate metabolism and on in vivo oxidative stress in type 2 diabetic mice. Mice (C57BL/KsJ-lepr(db)/lepr(db), db/db) were fed a diet containing 0%, 5%, or 10% BS based on AIN-93G for 21 d. Plasma parameters, such as total cholesterol, arteriosclerotic index, thiobarbituric acid reactive substances (TBARS), and the HbA1c concentration of whole blood in the diabetic BS-fed groups were lower than those in the diabetic control (AIN-93G) group. Concentrations of hepatic parameters, such as lipids, total cholesterol, triglyceride, and TBARS levels in BS-fed groups, were lower than those in the diabetic control group. Although gene expressions of the hepatic lipid regulation enzymes such as 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoAR) and cholesterol 7α-hydroxylase (CYP7A1) in diabetic BS-fed groups were higher than in the diabetic control group, the elevation of mRNA level of CYP7A1 was greater than that of HMG-CoAR. In addition, concentration of bile acids in feces was higher in the diabetic BS-fed groups than in the diabetic control group. These results suggest that BS have various in vivo activities in relation to antidiabetic effects in type 2 diabetic mice, especially for improvement in lipid metabolism. It was deduced that excretion of bile acids in feces by feeding the BS diet would contribute to the suppression of the cholesterol concentration in the plasma and liver tissues of mice.

Chiral separation of catechins in buckwheat groats and the effects of phenolic compounds in mice subjected to restraint stress.

This paper investigates the stereochemistry of catechin and epicatechin compounds in buckwheat ( Fagopyrum esculentum Moench) groats and then examines the effects of an orally administered mixture of the phenolic compounds isolated from the groats in restrained mice. Phenolic compounds separated by Sephadex LH-20 chromatography contained catechin and epicatechin compounds with a sugar moiety or esterified with phenolic acid derivatives along with rutin. Other unidentified major compounds in the HPLC chromatogram were also deduced on the basis of the spectrometric data with LC-MS/MS analysis to be catechin or epicatechin compounds. A chiral HPLC separation technique under normal-phase conditions showed that catechin and its derivative compounds in buckwheat groats were (+)-isomers, whereas epicatechin and its derivative compounds were (-)-isomers. Propylene glycol (PPG) or buckwheat groats phenolic compounds (BGP) in PPG (10 or 100 mg/kg of body weight) were administered intragastrically once per day for 3 days to mice, which were then restrained for 24 h. Unrestrained mice were given PPG solution with or without free access to feed and water. Restraint stress induced an elevation in plasma arteriosclerotic index, hepatic total cholesterol, and the amount of thiobarbituric acid-reactive substances (TBARS) in plasma and liver tissues. In contrast, these variables were suppressed in the restrained mice that were given BGP. These results suggest that BGP has in vivo antistress effects against the reactions induced by immobilization in mice.

Effect of low temperature on flavonoids, oxygen radical absorbance capacity values and major components of winter sweet spinach (Spinacia oleracea L.).

BACKGROUND Winter sweet treatment (WST) has been established for cultivating high-quality leafy vegetables during the winter. Although it is known that chilling stress during cold acclimation induces oxidative damage by reactive oxygen species in plant tissues, knowledge about changes in antioxidant activity and compounds during WST in spinach is superficial. We investigated changes in flavonoids, total ascorbic acid, carotenoids and hydrophilic oxygen radical absorbance capacity (H-ORAC) along with components in three spinach varieties during low-temperature treatment by exposure to cold air in winter. RESULTS The H-ORAC values increased substantially together with total flavonoids and total ascorbic acid concentration. In addition, WST increased mono- and diglucosylated flavonoid derivatives with an ortho-dihydroxy (catechol) structure of lower molecular weight in spinach. These results suggest that WST contributes to the prevention of low-temperature-induced oxidative damage by increasing the level of antioxidant compounds, thereby improving antioxidant activity. Although sucrose concentrations were increased by WST, nitrate and oxalate concentrations did not increase in any variety. CONCLUSION WST can contribute to the increase in antioxidant compounds such as flavonoids and ascorbic acids, antioxidant activity and sucrose without increasing in nitrate and oxalate of spinach.